Semiconductor fabrication processes involve patterning operations, including depositing and etching of various materials on a semiconductor substrate. Substrates include features of various types, including horizontal and vertical features, negative features with sloped sidewalls, features with re-entrant features, and features made as negative features in substrates having a multi-layered stack of two or more materials such that the composition of the material on the surface of sidewalls of the feature varies depending on the depth of the feature. Various techniques for filling such features exist, but as devices shrink and features become smaller, feature fill without voids or seams becomes increasingly challenging.